The disclosure of the following priority application is herein incorporated by reference:
Japanese Patent Application No. 2000-157973 filed May 24, 2000
1. Field of the Invention
The present invention relates to a shielding device for shielding the clearance between members moving relative to each other and, more particularly, to a shielding device for shielding from an optical beam, as might otherwise enter an optical device through a clearance between the lens-barrel and the body thereof, or for blocking water droplets or dust, as might otherwise immigrate through that clearance.
2. Related Art
In the prior art, the shading devices for blocking out the light, as might otherwise enter through the clearance between the two relatively moving members such as the camera body and the lens-barrel, have been disclosed in Japanese Laid-Open Patent Applications No. 6-222422 and No. 11-305286, for example.
These shading devices are constructed to include an annular (doughnut-shaped) shading member fitted slidably on the outer circumference portion of the photographic lens-barrel, and an annular support member for supporting the shading member. The shading member is made smaller in its internal diameter than the external diameter of the photographic lens-barrel and is fitted on the outer circumference of the lens-barrel. With this construction, the outer circumference portion and the shading member contact snugly with each other.
The shading members in the aforementioned shading devices of the prior art are generally constituted of a sheet of black rubber or artificial leather for giving it a shading effect. In order to improve the shading effect, the internal diameter of the annular shielding member has to be made so small as to raise the contact pressure of the shielding member against the lens-barrel.
There is also known a shielding device that is given a function to prevent the looseness of the lens-barrel by fixing the outer circumference portion of an annular shading member on the camera main body or the lens-barrel thereof. In this shielding device, the contact pressure between the shielding member and the lens-barrel may rise or drop where an eccentricity occurs between the camera main body and the lens-barrel or between a plurality of lens-barrels.
In the recent years, many products are coated on the appearances of the photographic lens-barrels in not only the black color of the known art but also metallic colors so as to express a metallic character considering the design and the impression of high quality. It is no exaggeration that the coated surface of the lens-barrel of this kind is like the file because the metallic coating contains aluminum powder.
In the case of photographic lens-barrel described above, the shading member slides on the surface of the photographic lens-barrel and is scraped off as it moves in the extending direction of the photographic lens-barrel relative to the camera body so that the filings stick to foul the surface of the photographic lens-barrel. Especially the aforementioned rise in the contact pressure makes a major cause for the fouling and has to be avoided because it may deteriorate the product image.
When the contact pressure is locally lowered by the aforementioned eccentricity, on the other hand, the clearance between the shielding member and the lens-barrel is easily formed to invite a poor shielding. In this sense, there is a contrary restriction on the excessive drop of the contact pressure for preventing the aforementioned fouling.
An object of the present invention is to provide a shielding device that is freed from having its tube member fouled by the sliding motions of the shielding member.
Another object of the present invention is to provide a shielding device which can prevent the tube member from being fouled by the sliding motions of the shielding device and which can be shielded more reliably even if the tube member is made eccentric.
In order to achieve the above-specified objects, the shielding device according to the present invention shields a clearance between a frame member having an opening and a tube member where is received in the opening and movable in the direction of an optical axis. The shielding device comprises an annular shielding member arranged between the inner circumference of the opening of the frame member and the outer circumference of the tube member. The annular shielding member is so slidably fitted on the tube member that its inner circumference may contact with the outer circumference portion of the tube member. The annular shielding member is either given substantially the same color as that of the outer circumference surface of the tube member or made substantially transparent at least at its portion having contact with the tube member.
In case that the shielding member is fixed at its outer circumference portion in the frame member and its inner circumference portion to contact with the outer circumference portion of the tube member is fitted slidably on the tube member, a shading member may be deformable at least radially with respect to the tube member. It is preferable that the shielding member has a shading property at its portion having no contact with the tube member. The contact pressure of the shading member to contact with the tube member is lower than that of the shielding member to contact with the tube member.
When the invention is applied to the camera, the frame member is a camera body, and the tube member is a lens-barrel.
The shielding member may include a low-friction layer having contact with the outer circumference portion of the tube member.